Category learning is a basic cognitive function for humans and non-human animals and a sharp focus in human and animal research. The proposed research would integrate these two research traditions in several ways. It would 1) create an experimental platform that lets human and animal category learning be closely compared; 2) advance the study of exemplar processes and prototype formation in nonhuman primates' categorization using selected human paradigms; 3) search for (dis)continuities between human and primate category learning; 4) search, in particular, for constraints on primate category learning; 5) ask, using human dissociative paradigms, whether primates have differentiable category learning systems analogous to those called explicit and implicit in humans; 6) evaluate the organizing hypothesis that monkeys somewhat lack humans' explicit categorization system; 7) refine, based on the overall pattern of human and animal findings, hypotheses about the role of verbalization and explicit cognition in categorization; and 8) foster a dialog between comparative researchers and researchers of the cognitive neuroscience of category learning. The possibility of dissociable category-learning systems with different phylogenetic distributions has implications for comparative and cognitive psychology and for theories of the evolution of the primate mind. Research on dissociable learning systems could also contribute to developmental psychology and cognitive neurosicence because different systems could be pre-eminent at different ages or relatively impaired/preserved in clinical conditions like Parkinson s disease, Alzheimer's disease, depression, schizophrenia, and the amnesic syndromes. Moreover, by carefully comparing humans' and animals' categorization competencies/limitations one might advance theory in neuroscience by correlating these with the differential development of the brain systems thought to serve category learning. The research could also suggest training regimens that would foster greater learning in particular child or adult populations by capitalizing on preserved capacities. The research also bears on the role of language in category learning and problem solving, on possible limits on these capacities in children with language disorders, and on possible implicit compensatory approaches.